The San Antonio Cancer Institute Flow Cytometry Core Facility is located within the University of Texas Health Science Center at San Antonio (UTHSCSA) Institutional Flow Cytometry Facility. The core includes a state-of-the-art rapid cell sorter (FACSstar Plus; 10,000 events/sec) and a new FACScalibur instrument for 3-4 color analysis. The facility is equipped with two workstations and two advanced printers (Tektronix). The Director of the combined facilities is Dr. Yair Gazitt (Medicine/Hematology, UTHSCSA), who has used flow cytometry for analysis and sorting since 1977 and has been the Director of the institutional Flow Cytometry Core Facility for the past five years. The core supports cell sorting and cloning of specific subpopulations of lymphocytes, various tumor cells, osteoclasts, osteoblasts, stem cells and kidney cells. This includes mouse models and human studies. Basic services offered to the San Antonio Cancer Institute consist of immunophenotyping (including leukemia, lymphoma breast cancer cells), DNA content and cell cycle analysis (including apoptosis analysis), cell sorting, multiparameter analysis (3-3 color), Ca++ fluxes, measurement of MDR-1 function and apoptosis. The facility has been instrumental in the success of several key established Cancer Center investigators and work is ongoing to develop new techniques in response to needs identified by SACI members. Protocols currently under development include sorting by DNA content and multiparameter cytokine quantitation using fluorescent microspheres (Becton Dickinson), a fluorescence based "ELISA" assay.